DE69328788T2 - REDOX COPOLYMERS AND THEIR USE IN THE PRODUCTION OF MIXED CONDUCTIVE MATERIAL - Google Patents

Description

The present invention relates to copolymers and their use for producing materials with mixed conductivity.

Polymer electrolytes are known which are obtained by dissolving a salt in a solvating polymer comprising heteroatoms. Such electrolytes, which have ionic conductivity and whose solvent is a polyethylene oxide or an ethylene oxide copolymer, are described, for example, in EP-A-13.199 (M. Armand, M. Duclot). These polymer electrolytes have numerous fields of application, in particular in the field of electrochemical power generators, light modulation systems (M. Armand et al., EP-87401555), transducers, for example for selective or reference membranes (A. Hammou et al., FR 86.09602).

Materials are also known that have mixed conductivity, i.e. in which a simultaneous displacement of ions and electrons takes place. These materials can be so-called insertion materials, among which can be mentioned those materials that are formed by dissolving lithium in a disulfide, for example titanium disulfide, or in an oxide, for example the vanadium oxides VOx (x ≥ 2.1) and manganese oxides. Such materials are of interest as electrode materials. The energy they can store per unit mass is high, but their kinetics and their performance can be limiting. In addition, they can be destroyed by overcharge or over-discharge.

Mixed conductivity in heterogeneous phases is achieved by dispersing conductive particles, such as carbon blacks, in polymers, for example by dispersing carbon black in ion-conducting polymers. These mixtures are used in particular in electrochemical power generators to achieve a good exchange of ions and electrons with the electrode materials, such as the built-in compounds. It is nevertheless difficult to achieve complete penetration at the microscopic level with these mixtures. In particular, the carbon blacks increase the viscosity of the compositions considerably, which leads to poor wetting of grains from the electrode material. material and the presence of residual porosity, which increases the apparent resistance of the medium.

Polymers are also known that have conjugated π-bonds and are essentially ionic. They become conductive after the incorporation of ionic (anion or cation) species that compensate for the loss or gain of electrodes of the network of π-orbitals. These materials have metallic conductivity and are not solvents. The mobility of ionic species that serve to compensate for charges is very low due to the rigidity of the polymer network. In addition, the molding of these materials is difficult due to their infusible and generally insoluble nature.

From M. Watanabe et al., Electrochimica Acta 37(9), 1521 (1992), materials with mixed conductivity (hereinafter mixed conductivity) are known, which are obtained either by dissolving LiClO4 and LiTCNQ in a polyethylene oxide or by radical copolymerization of vinylferrocene and oligoethylene glycol acrylic acid esters. The statistical copolymers obtained have a reduced range of chemical and electrochemical stability, and the only redox molecules that can be used are redox molecules that are active in radical polymerization, which considerably limits the choice of materials. In addition, the resulting comb structure of the polymer hardly allows the units carrying redox functions to form a packing that favors electron exchange.

EP-A-0.033.015 discloses polymers formed from naphthalene diimide units linked by segments comprising 0 to 3 alkylene oxide units or by segments comprising 1 to 5 alkylene imine units, the alkylene group in both cases having between 1 and 4 carbon atoms. Such polymers have good electronic conductivity due to the fact that the alkylene oxide or alkylene imine segments enable packing of the redox functions. However, linker segments are too short to provide the polymer with the solvation properties necessary to impart ionic conductivity.

The aim of the present invention is to provide macromolecular materials which have good mixed conductivity properties and good mechanical properties at the same time.

For this purpose, the present invention relates to copolymers.

The invention also relates to materials with mixed conductivity, the solvent of which consists essentially of at least one of the above-mentioned copolymers.

Finally, the invention aims at various applications of these copolymers and materials with mixed conductivity.

A copolymer according to the present invention is a segmented copolymer consisting essentially of identical or different organic segments A having a valence i, where 1 ≤ i ≤ 6, and identical or different organic segments B having a valence j, where 1 ≤ j ≤ 6, characterized in that the segments B have redox properties, that the segments A are solvating segments selected from homopolymers of ethylene oxide or propylene oxide, copolymers of ethylene oxide and propylene oxide and copolymers of ethylene oxide or propylene oxide with a comonomer polymerizable by forming ether bonds, characterized in that each segment A is linked to at least one segment B via a group Y and each segment B is linked to at least one segment A via a group Y, wherein the group Y is made up of ether, thioether, secondary amino, tertiary amino, secondary amide, tertiary amide, imide, quaternary ammonium and carbon-carbon bonding groups. and that the weighted molar average of i and the weighted molar average of j are each ≤ 2.

Segment B contains at least one unit derived from an aromatic molecule which can easily form stable anionic or cationic radical species by losing or gaining at least one electron. Particularly suitable units derived from an aromatic molecule include aromatic tetracarboxylic acid diimido groups, for example the pyromellitic acid diimido group, the benzophenonetetracarboxylic acid diimido group, the 1,4,5,8-naphthalenetetracarboxylic acid diimido group and the 3,4,9,10-perylenetetracarboxylic acid diimido group. Quaternary aromatic dications can also be mentioned, for example 4,4'-dipyridinium or trans-1,2-bis(pyridinium)ethylene. Substituted aromatic diamino groups may also be mentioned, for example the 1,4-phenylenediamino group or the 4,4'-stilbenediamino group. Alkyldiarylamino groups with condensed nuclei may also be mentioned, for example the 9,10-dicarbylphenazino group or the N,N'-bisacridino group. Finally, groups derived from aromatic hydrocarbons, for example 9,10-bis(methylene)anthracene, and metalocenediyls, for example 1,1'-ferrocenediyl, may be mentioned.

It is understood that the B segments that can be used are not limited to the above-mentioned examples, but can also be selected from their homologues, obtained by substituting hydrogen atoms by carbon-containing groups, by inserting carbon-containing groups that allow the conjugation of the electron system to be maintained between the redox groups or by replacing hydrocarbon groups by heteroatoms (for example by replacing HC by N).

The formulas of the various specific groups B mentioned above are given below:

When the solvating segment A is a copolymer, the comonomer can be selected from oxymethylene, oxetane, tetrahydrofuran, methyl glycidyl ether and dioxolane. Of the copolymers, those containing at least 70 mol% of units derived from ethylene oxide or propylene oxide are particularly preferred. The solvating segments can also be selected from polyimines.

In order for the homopolymers and copolymers referred to above as solvating segment A to actually have ion conduction properties resulting from the solvating properties, it is necessary that at least some of the segments A of a polymer comprise a sufficient number of solvating units to surround a cation according to its coordination number. The number of solvating units increases in particular with the diameter of the ion to be solvated and the space required by the redox segment B present. The determination of the number of solvating units that a segment A must carry in order to bring about the solvation necessary to impart sufficient ionic conductivity to the polymer is within the capabilities of those skilled in the art. By sufficient ionic conductivity is meant a conductivity which is at least 10-8 S.cm-1 at ambient temperature. By way of illustration: for a redox segment of the pyromellitic acid diimido type, the number of ether-type solvating units is at least 3; for a redox segment of the perylenetetracarboxylic acid diimido type, the number of ether-type solvating units must be at least 8; for a redox segment of the naphthalenetetracarboxylic acid diimido type, the number of ether-type solvating units must be at least 5. Hereinafter, the term "solvating segment" refers to segments which meet these conditions and which make it possible, in particular, to obtain an ionic conductivity of at least 10-8 S.cm-1 at ambient temperature.

The segments A may also comprise a group that enables the formation of a network. Examples of such a group may be those groups which enable radical cross-linking, Diels-Alder cross-linking or polycondensation, for example by hydrolysis of an alkoxysilane group. These special segments A are referred to below as segments A'.

In a copolymer according to the present invention, a part of the non-solvating segments A can also be replaced by non-solvating segments A" of the arylene or alkylarylene type if the interactions between the redox units B are to be strengthened.

An advantage of the copolymers according to the present invention is that they can be obtained by polycondensation processes based on relatively simple chemical reactions that depend on the nature of the group Y that serves as a link between a segment A and a segment B.

In general, a copolymer according to the present invention is obtained by reacting at least one compound AZi with at least one compound BXj or at least one compound AXi with at least one compound BZj, where A, i, B and j have the meaning given above, the groups Z and X are selected according to the desired group Y, the relative proportions of the various AZi (or AXi) are such that the ratio between the number of residues Z (or X) and the number of segments A is at least 2, the relative proportions of the various BXj (or BZj) are such that the ratio between the number of residues X (or Z) and the number of segments B is at least 2.

In a specific embodiment, X is a leaving group and Z is a nucleophilic group.

The leaving group X can be a halide, in particular a chloride, a bromide or an iodide, or a sulfate R'OSO₃ or a sulfonate R'SO₃, where R' is an organic group having less than 20 carbon atoms. Preferably R' represents an alkyl group, an aryl group or an alkylaryl group, it being possible for these groups to be optionally halogenated. The leaving group can also be formed by an anhydride group, a dibasic acid group or a monobasic acid group. The leaving group can also be formed by an onium salt, for example a diphenylpyridinium salt.

A linking group Y of the ether or thioether type can be obtained starting from a nucleophilic group Z selected from the groups -OM or -SM (where M represents an alkali metal).

An imide-type linking group Y can be obtained by reacting a leaving group X formed by an acid anhydride with a nucleophilic group Z which is an amine, followed by dehydration. It can also be obtained by a transimidation process starting from an aromatic molecule comprising i imide groups by reacting with a compound A(NH)i. In addition, a diimide linking group can be obtained by reacting an amine with a diacid or by reacting a compound AXi with an alkali metal salt of a compound BZj, wherein Z represents an imide group.

A secondary amine-type linking group can be obtained by reacting a leaving group with a nucleophilic primary amino group.

A tertiary amine-type linking group can be obtained by reacting a leaving group with a nucleophilic secondary amino group.

A secondary amide-type linking group can be obtained by reacting a leaving group with a nucleophilic primary amide group.

A tertiary amide-type linking group can be obtained by reacting a leaving group with a nucleophilic secondary amide group.

A quaternary ammonium-type linking group can be obtained by reacting a leaving group with a nucleophilic tertiary amino group.

When the group Y is a carbon-carbon bond, the copolymer can be obtained by reacting an organometallic compound as a precursor of segment A with a compound containing a leaving group as a precursor of segment B, or vice versa, the reaction being catalyzed by a coordinative complex of a transition metal, such as nickel or cobalt, the coordination being ensured by a phosphine.

The properties of a copolymer according to the present invention can be predetermined by the selection of the segments A and/or the segments B.

A copolymer according to the present invention can comprise identical A segments. It can also comprise different A segments. The choice of the solvating A segments makes it possible to reduce or even eliminate the crystallinity of the copolymer and thus improve its ionic conductivity. It can also improve its mechanical properties. The introduction of non-solvating segments makes it possible to adapt certain properties of the copolymer, for example its mechanical properties or the conductivity of the network; it also makes it possible to introduce new properties inherent in the non-solvating segments, such as adhesion, or chemical groups.

If, in view of the intended use of a copolymer according to the present invention, it is desirable that the copolymer be able to form a network, two solutions are possible. Part of the segments A can be replaced by segments A' comprising crosslinkable groups as defined above. Part of the segments B can also be replaced by segments B' which do not have redox properties but comprise groups which enable crosslinking. In both cases, these can be radical cross-linking, Diels-Alder cross-linking or polycondensation, for example by hydrolysis of an alkoxysilane group. To this end, during the preparation of the copolymer, some of the BXj molecules are replaced by B'Xi molecules, in which B' is a residue with valence j' and which do not have a redox function but have cross-linkable functionalities, or at least some of the AZi molecules are replaced by A'Zi' molecules which have a cross-linkable group. The stoichiometry of the reaction must therefore take into account all of the X and Z groups supplied by the co-reactants.

The copolymers obtained in this specific case consist of identical or different organic segments A, each having a valence i, where: 1 ≤ i ≤ 6, of identical or different segments B, where B is each an organic radical having redox properties and a valence j, where: 1 ≤ j ≤ 6, and of segments A' having a valence i', where: 1 ≤ i' ≤ 6, or of identical or different segments B' having at least one crosslinking-enabling group having a valence j', where: 1 ≤ j' ≤ 6;

- wherein each segment A or A' is connected via a group Y to at least one segment Bj or B'j, wherein each segment B or B' is connected via a group Y to at least one segment A or A', wherein the group Y is as defined above ;

- where the weighted molar average of the valences i and i' of the segments A and A' and the weighted molar average of the valences j and j' of all residues Z and Z' are each approximately ≥ 2.

The copolymers according to the present invention can be used as such or in cross-linked form for the production of mixed line materials.

The mixed line materials according to the present invention consist essentially of a readily dissociable salt and a copolymer according to the present invention.

If the degree of polycondensation of a copolymer according to the present invention is sufficient, the copolymer as such can be used to produce a mixed piping material. However, its use is not easy.

To produce mixed line materials, it is preferred to use copolymers with a relatively low degree of polycondensation, such as those obtained from one or more compounds AZi and one or more compounds BX (and optionally one or more compounds A'Zi' or B'Xj'), in which the weighted molar average for both i (or i + i') and j (or j + j') is practically 2. Such copolymers are crosslinked after molding by means of crosslinkable groups present on the A' and/or B' segments.

When producing mixed line materials, it is necessary to use copolymers in which at least part of the segments A are solvating segments. The solvating segments A consisting of homopolymers of ethylene oxide or propylene oxide or copolymers of ethylene oxide or propylene oxide with a comonomer polymerizable by forming ether bonds, in which the comonomer represents a maximum of 30 mol%, are particularly preferred. The copolymers of ethylene oxide and propylene oxide are particularly interesting.

The salt introduced into the copolymer before cross-linking or into the cross-linked polymer is chosen from those salts commonly used for solid materials with ionic conductivity. As an example, mention may be made of salts (1/mM)⁺X³⁻, in which M represents a proton or an ion of a metal with valence m, selected from alkali metals, alkaline earth metals, transition metals and rare earths, or an ammonium, amidinium or guanidinium ion; in which X³ represents an anion with delocalized electron charge, for example Br⁻, ClO₄⁻, AsF₆⁻, RFSO₃⁻, (RF-SO₂)₂N⁻, (RFSO₂)₃C⁻ wherein RF represents a perfluoroalkyl or perfluoroaryl group, in particular a perfluoroalkyl or perfluoroaryl group having a maximum of 8 carbon atoms, in particular CF₃⁻ or C₂F₅⁻.

The salt can also be selected from salts of the formula (1/nM)+[(RFSO₂)₂CY¹]⁻, wherein Y¹ represents an electron withdrawing group selected from -CN and the groups R"Z¹⁻, where Z¹ represents a carbonyl group, a sulfonyl group or a phosphonyl group and R" represents a monovalent organic group optionally containing a group crosslinkable radically or via a Diels-Alder reaction, wherein M and RF have the above meaning. Such compositions can be prepared by reacting a compound (1/nM)⁺[(RFSO₂)₂CH]⁻ with a compound Y¹X¹ in the presence of an aprotic nucleophilic base Nu, where X¹ represents a halogen or a pseudohalogen. The lithium salts are particularly preferred, in particular (CF₃SO₂)₂N⁻Li⁺ and (CF₃SO₂)₃C⁻Li⁺. Mixtures of salts can also be used. These salts and their preparation process are described in FR 91.13789, filed on November 8, 1991.

A mixed line material according to the present invention in which the copolymer according to the present invention is cross-linked is obtained by subjecting the copolymer to the action of heat or energetic radiation, such as UV radiation, γ-radiation or electron beam, optionally in the presence of a radical initiator. The radical initiator can be selected, for example, from benzoyl peroxide, azobisisobutyronitrile (AlBN), azobiscyanovaleric acid, dicumyl peroxide (Dicup) or disulfides, e.g. 3,3'-dithiodipropionic acid. The salts (1/nM)+[(RFSO₂)₂CY¹]⁻ defined above, where Y¹ contains a source of free radicals, can be used as radical initiators. The radical initiator is not necessary if crosslinking occurs via a Diels-Alder reaction.

According to a first embodiment, a mixed line material is obtained by dissolving the copolymer, the salt and optionally a radical initiator in a common solvent. The amount of initiator used is advantageously from 0.1 to 5% by weight relative to the copolymer. The solvent is selected from volatile solvents; examples of such a solvent include acetonitrile, tetrahydrofuran and acetone. The viscous solution obtained is degassed and then spread on a suitable support, for example a PTFE plate. After evaporation of the solvent, the film obtained is heated for 4 hours at a temperature between 70°C and 120°C (depending on the initiator used).

Another type of cross-linking involves first cross-linking the copolymer in the absence of salt and then preparing a membrane. The salt is then introduced into the membrane in the following way: a highly concentrated salt solution is prepared in a volatile polar solvent, it is allowed to be absorbed by the membrane and then the solvent is evaporated. The amount of salt introduced is determined by the difference between the initial weight of the membrane and its final weight.

According to a third embodiment, the crosslinking of a copolymer according to the present invention is carried out using a radical polymerization initiator in the presence of a monomer carrying an ionic group and a radically crosslinkable group. Examples of such monomers are described in FR 92.02027 filed on February 21, 1992.

It is understood that the mixed conduction materials of the present invention may also contain additives that are commonly used in ion-conducting materials, such as plasticizers and stabilizers, depending on the final properties desired.

The mixed line materials of the present invention are easily prepared and their use is facilitated by the good solubility prior to crosslinking when the respective weighted mole average of i and j is not greater than about 2.

A material obtained from a copolymer according to the invention can, due to the redox activity associated with good ionic conductivity, be used advantageously as an active component of an electrode, alone or in a mixture with incorporating compounds, for generators which are completely solid or for generators whose electrolyte is either softened or in the form of a gel consisting of a polymer and a liquid solvent. When such a material is used in a mixture with an incorporating compound, the rapid kinetics of the electron exchange enable it to replace in whole or in part the agent used to ensure electronic conductivity, in particular soot. In addition, it provides a reserve of capacity and in particular a reserve of power for this type of generator. This possibility is particularly advantageous when the material according to the invention is used in an anode by choosing a copolymer with a redox potential slightly lower than that of the incorporating material. Under these conditions, the redox copolymer regains its initial capacity after the power demand ends.

The materials comprising the copolymers according to the invention also make it possible to improve the functioning of the electrochemical generators and to avoid their premature wear. The inclusion of a redox copolymer, the voltage of which is suitably chosen, in at least one of their electrodes makes it possible to indicate the end of the charging or discharging process by reading the EMF, so as not to degrade the system. Similarly, the use of a copolymer according to the invention in a composite electrode makes it possible to modulate the voltage window in which the electron exchange can take place. Advantageously, the mixed conducting material contains a copolymer according to the invention, chosen so as to improve its electron conductivity. ability at the end of the recharging of the mounting material contained in the composite electrode.

In the materials according to the invention, the injection (reduction) or the withdrawal (oxidation) of electrodes is accompanied by a color change. This property enables them to be used as a cathode of a light modulation device, in particular for glazing or electrochromic coatings. The film-forming property of copolymers according to the invention is particularly advantageous for their use in this specific application. The various segments constituting the copolymer can be chosen so that the copolymer can be cross-linked or polycondensed after molding and so that it adheres well to the support (generally made of glass or an oxide layer) by melting.

Finally, the mixed conduction materials according to the present invention can be advantageously used to eliminate static electrical charge due to their electronic conductivity.

The present invention is illustrated by the following examples, which are given by way of illustration and not by way of limitation.

EXAMPLE 1

21.8 g of pyromellitic anhydride and 63.5 g of O,O'-bis-(2-aminopropyl)poly(oxyethylene 500) (Jeffamine® ED600), commercially available from Texaco, are dissolved in 200 ml of a mixture of equal volumes of pyridine and acetonitrile. The mixture is stirred at ambient temperature for 5 hours, during which the polyamic acid is formed by the action of the amino groups on the cyclic anhydride groups. 50 ml of acetic anhydride are then added to the mixture, which allows the acid amide groups to be converted into imide rings. Stirring is continued for 2 hours. The resulting polymer is precipitated by dissolving the reaction mixture in 800 ml of diethyl ether which is kept at -10ºC. The polymer is purified by dissolving three times in acetone and precipitating in ether at -10ºC.

EXAMPLE 2

4.4 g of poly(ethylene oxide) with a molecular weight of 9 x 105 are dissolved in 80 mL of anhydrous dichloromethane, the procedure being carried out in a glove box under an argon atmosphere containing ≤ 1 vpm of oxygen and water vapor. The solution is cooled to -15°C and a solution of 1.87 mL of trifluoromethanesulfonic anhydride in 10 mL of hexane is added with stirring. A cleavage reaction takes place to form an oligooxyethylene glycol triflate with an average molecular weight of 900. To the reaction mixture is added 1.73 g of 4,4'-dipyridyl as a solution in 10 mL of dichloromethane. Stirring is continued at -15°C for 2 h and the reactor is allowed to return to ambient temperature. Stirring is continued for 8 h. The solvent (dichloromethane + hexane) is partially eliminated using a rotary evaporator, leaving about 30 ml of a cloudy suspension. The polymer is precipitated with anhydrous ether and purified by 4 cycles of dissolution/precipitation in the solvent: acetonitrile / non-solvent: ether pair.

EXAMPLE 3

3.92 g of 3,4,9,10-perylenetetracarboxylic anhydride and 6.35 g of O,O'-bis-(2-aminopropyl)poly(oxyethylene 800) (Jeffamine® ED900), commercially available from Texaco, are dissolved in 30 ml of dimethylacetamide. In a reactor equipped with a mechanical stirrer, the mixture is heated to 160°C under argon for 3 h. The resulting red-colored polymer is precipitated by pouring the reaction mixture into 200 ml of a diethyl ether/hexane mixture. It is then purified by ultrafiltration in water using a membrane whose cutoff is at MW = 5000. The electroactivity of this material is verified by voltammetry using microelectrodes. The electrochemical chain is as follows:

The speed and reversibility of inserting electrodes with Eo = 2.6 and 2.4 V / Li : Liº into the material is demonstrated. This polymer also exhibits pronounced electrochromic properties, changing from ruby red in the neutral state to dark violet after reduction.

EXAMPLE 4

This example illustrates the possibility of preparing the polymer by a transimidation process. 27 g of 1,4,5,8-naphthalenetetracarboxylic anhydride are treated with 17 ml of propylamine in 50 ml of pyridine. After the reaction to form the acid amide by opening the anhydride rings, 25 ml of acetic anhydride are added. The N,N'-bispropylnaphthalenetetracarboxylic imide is precipitated by water and purified by recrystallization from ethanol.

To 19.32 g of imide are added 42.5 g of O,O'-bis-2-(aminopropyl)poly(oxyethylene 800) (Jeffamine® ED900) and 2.2 g of bicyclo-[2,2,2]-oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (crosslinker) in 150 mL of anhydrous dimethylacetamide. In a reactor equipped with a mechanical stirrer, the mixture is heated to 160ºC in an argon stream for 3 h. The resulting brown polymer is precipitated by pouring the reaction mixture into anhydrous ether maintained at -10ºC. The material is purified by three consecutive dissolution/precipitation operations in the solvents dichloromethane/ether. The polymer is radically crosslinkable by a process that acts on the bicyclo-[2,2,2]-oct-7-ene-2,3,5,6-tetracarboxylic acid diimido groups.

EXAMPLE 5

15.62 g of 4,4'-dipyridyl, 26.2 g of itaconic acid and 100 ml of an aqueous 2 m solution of trifluoromethanesulfonic acid are heated at reflux for 4 h. The solution is evaporated under reduced pressure and the resulting solid is purified by recrystallization from isopropanol. It has the following structure:

7.16 g of the above compound, 5.71 g of O,O'-bis-(2-aminopropyl)poly(oxyethylene 500) (Jeffamine® ED600) and 0.207 g of bis(aminopropyl)dimethoxysilane are dissolved in 30 ml of dimethylformamide. 10 ml of pyridine and 5 g of dicyclohexylcarbodiimide are added. The mixture is stirred under argon for 30 h at ambient temperature. The polymer formed has mainly the following structure:

EXAMPLE 6

An electrochromic system is provided, the structure of which is schematically shown in Fig. 1. The electrochemical system shown in Fig. 1 comprises a glass substrate (1), a layer of doped zinc oxide (2), a polymer layer (3), an electrolyte (4), a counter electrode (5), a zinc oxide layer (6) and a glass substrate (7). 0.5 g of the polymer of Example 6 are dissolved in 3 ml of dimethylformamide together with 80 mg of lithium trifluoromethanesulfonate. The solution is applied using a spin coating process to obtain a 1 µm layer (3) on a flat glass substrate (1) previously coated by reactive cathode etching. sputtering with a 120 nm thick layer of zinc oxide doped with aluminium (2). The film (3) is cross-linked by treatment in air at 60ºC for 2 hours. The counter electrode (5) consists of an equimolar 50/50 mixture of cerium oxide and titanium oxide, which is deposited by a sol-gel process to form a layer with a thickness of 200 nm over a layer (6) of zinc oxide, analogous to layer (2) on glass (7). The mixed oxide of cerium and titanium is previously reduced with lithium by electrochemical insertion at 5 x 10⊃min;² Coulomb. The two electrodes are separated by an electrolyte (4) obtained by polycondensation of poly(ethylene glycol) (MW 1,500) with chloromethyl-2-chloropropene-3 in which bis(trifluoromethylsulfonyl)imide lithium is dissolved at a concentration of 1 mole of salt per 18 oxyethylene units.

The electrochromic system, in which the redox polymer is the cathode, operates when a voltage of 1.5 volts is applied. A blue color appears within a few seconds; it is stable when the circuit is open and disappears when the electrodes are short-circuited. A similar device can be made by replacing the glass substrate with a polymer film of the PET or polysulfone type.

EXAMPLE 7

25 g of α,ω-dibromo-ligooxyethylene are prepared from polyethylene glycol of MW 1000 by reaction with an excess of thionyl bromide in acetonitrile in the presence of a basic ion exchange resin of the Amberlyst® A21 type (Rohm & Haas). The reaction mixture is filtered and the polymer is precipitated in ether cooled to -10°C. Purification is also carried out by dissolution/precipitation in a dichloromethane-ether pair. An analysis of the molecular weight by steric exclusion chromatography and determination of the halogen content (AgNO₃/AgBr) gives a functionality of 2 and an average molecular weight MW = 1035. 3.53 g of phenazine are dissolved in 15 ml of anhydrous THF and 0.5 g of metallic lithium are added under an argon atmosphere. The mixture is stirred using a polyethylene-coated magnetic rod. After the reaction, a yellow precipitate appears from the salt of the dianion. The excess of metallic lithium is separated and 14.49 g of α,ω-dibromo-ligooxyethylene, as previously prepared, are added; the mixture is stirred at ambient temperature for 20 h and the reaction product is precipitated in ether. The polymer obtained is purified in water using an ultrafiltration membrane with a cutoff of MW = 5,000. The water is evaporated and a brown-green colored polymer is obtained. The complex formed by dissolving bis(trifluoromethylsulfonyl)imide-lithium has a reversible redox activity of + 3.5 V/Li:Liº.

EXAMPLE 8

525 mg of α,ω-bis(aminopropyl)poly(tetrahydrofuran) 750 are dissolved in acetonitrile and 640 mg of triphenylpyrilium trifluoromethylsulfonate are added. The formation of the trifluoromethylsulfonate of α,ω-bis(triphenylpyridiniumpropyl)polytetrahydrofuran 750 occurs spontaneously. The polymer is precipitated with water and then dried in vacuo at 40°C. 0.832 g of this material is dissolved in 5 ml of anhydrous THF and added to 194 mg of dilithiophenazine prepared as in Example 7. The resulting polymer is precipitated with water and purified by dissolution/precipitation in the solvent pair THF/water, then dichloromethane/ether. After drying, an elastomer is obtained which, like that in Example 7, has redox properties, with oxidation occurring between 3.2 and 3.6 V / Li : Liº.

EXAMPLE 9

An electrochemical generator is formed with a cathode of metallic lithium 18 µm thick laminated on a current collector of polypropylene (8 µm) metallized with 150 nm of molybdenum. The electrolyte consists of a copolymer of ethylene oxide with allyl glycidyl ether, which allows cross-linking, in the form of a 40 µm film and loaded with bis(trifluoromethylsulfonyl)imide-lithium to obtain an O/Li ratio of 14. The anode contains 55 vol.% of the polymer of Example 3 after dissolution of bis(trifluoromethylsulfonyl)imide-lithium at a concentration of 1 mole of salt per 14 oxyethylene units, 40 vol.% of lithium manganite Li0.2Mn₂O₄ and 5% by weight of Ketjenblack® carbon black (AKZO Chemicals). The composite material is dispersed and ground in acetonitrile and spread on a current collector identical to that of the cathode to form a film 95 µm thick. The electrochemical system is assembled by lamination. The use of a mixed conduction polymer for the anode makes it possible to obtain higher electrical power for a few tens of seconds (J = 2 mA.cm-2 at V = 2.5 V and 60ºC), the kinetics of the formation of radical anions inside the polymer being faster than those corresponding to the diffusion of lithium ions in the incorporation material. The electronic conductivity also makes it possible to reduce the carbon content in the composition, which provides an advantage in terms of weight and lower porosity of the film.

EXAMPLE 10

7 g of poly(oxyethylene glycol) with MW 1,000 are dehydrated by reaction with 1 ml of 2,2-dimethoxypropane and distillation of the excess reactants and reaction products in vacuo. The polymer is dissolved in 40 ml of anhydrous THF and 350 mg of sodium hydride is added. After the reaction has ended, which can be observed by the end of the evolution of hydrogen, 2.75 g of bis(9,10-dichloromethyl)anthracene is added. A sodium chloride precipitate is immediately observed. After the reaction has ended within a few hours, the suspension is centrifuged and the supernatant is precipitated with cold ether. The polymer is purified by ultrafiltration in water using a membrane with a cutoff of 5,000. After evaporation of the solvent, a soft material is obtained which has a redox activity of +1.4 V/Li:Liº with formation of a radical anion polymer Anth- and of +3.4 V/Li:Liº with formation of a radical cation polymer Anth+.

EXAMPLE 11

The lithium salt of 1,1'-bismercaptoferrocene is prepared according to the method of F. Brandt & T. Rauchfuss [J. Am. Chem. Soc. 114, 1926 (1992)1; 12 mmol of this salt in anhydrous THF are reacted with 13.2 g of α,ω-dibromo-ligooxyethylene, which is prepared from starting from polyethylene glycol of MW 1,000 according to Example 7. The mixture is stirred at 60ºC for 3 hours. The polymer obtained is eluted on a column containing a mixture of macroporous (cationic and anionic) ion exchange resins so as to remove the lithium bromide formed. The polymer is precipitated with ether and purified by solution/precipitation (dichloromethane/ether). The material has a redox activity of + 2.5 V / Li : Liº.

EXAMPLE 12

2 g of Jeffamine® ED2000 and 0.55 g of footen (buckminsterfullerene) C₆₀, commercially available from Aldrich, are mixed as solutions in toluene. The solution is poured into a glass ring (diameter: 40 mm) placed on a polished PTFE disk. After a few hours, the solution gels. Evaporation of the solvent gives an elastic solid with a dark yellow color, which has a redox activity of +2.4 V / Li : Liº.

EXAMPLE 13

An electrochemical generator is formed according to Example 9. The composition of the anode is modified to contain 55 vol.% of the polymer from Example 7 after dissolution of bis(trifluoromethylsulfonyl)imide lithium in a concentration of 1 mol of salt per 18 oxyethylene units and 14 vol.% of lithium cobaltite Li0.3CoO2. The discharge curve of this generator shows that the discharge kinetics below the potential of Elimit = 3.4 V are very slow due to the fact of the disappearance of the electronic conductivity of the redox polymer. The kinetics are maximum in the range of voltage of 3.5-3.7 V.

EXAMPLE 14

An electrochemical generator comprises a polymer electrolyte according to Example 9. The two electrodes are symmetrical and consist of a film of the polymer of Example 8 with a thickness of 10 µm loaded with potassium trifluoromethylsulfonate, which is deposited on current collectors made of polypropylene (8 µm) coated with 20 nm nickel metallized. The generator is assembled by lamination. It has a power of 0.05 coulomb per cm² at a voltage of 2 V with very fast kinetics. This type of generator can be used as a "supercapacitor" to supply or store suddenly increased electrical power.

Claims (15)

1. Segment copolymer in which the main chain consists of identical or different organic segments A with a valence i, where: 1 ≤ i ≤ 6, and of identical or different segments B with a valence j, where: 1 ≤ j ≤ 6, characterized in that the segments B have reversible redox properties and contain at least one unit derived from an aromatic molecule that can form stable anionic or cationic radical species by donating or accepting at least one electron, wherein at least some of the segments A are solvating segments selected from homopolymers of ethylene oxide or propylene oxide, copolymers of ethylene oxide and propylene oxide and copolymers of ethylene oxide or propylene oxide with a comonomer polymerizable by forming ether bonds, wherein each segment A is connected to at least one segment B via a group Y and each segment B is connected to at least one segment A via a group Y, wherein the group Y consists of ether, thioether, secondary amino, tertiary amino, secondary amide, tertiary amide, imide, quaternary ammonium and carbon-carbon bond-containing groups is selected and that the weighted mole average of i and the weighted mole average of j are each 2. 2. Copolymer according to claim 1, characterized in that the unit derived from an aromatic molecule is selected from aromatic tetracarboxylic acid diimido groups, for example the pyromellitic acid diimido group, the benzophenonetetracarboxylic acid diimido group, the 1,4,5,8-naphthalenetetracarboxylic acid diimido group and the 3,4,9,10-perylenetetracarboxylic acid diimido group. 3. Copolymer according to claim 1, characterized in that the unit derived from an aromatic molecule is selected from quaternary aromatic dications, for example from 4,4'-dipyridinium and trans-1,2-bis(pyridinium)ethylene. 4. Copolymer according to claim 1, characterized in that the unit derived from an aromatic molecule is selected from substituted aromatic diamino groups, for example the 1,4-phenylenediamino group and the 4,4'-stilbenediamino group. 5. Copolymer according to claim 1, characterized in that the unit derived from an aromatic molecule is selected from alkyldiarylamino groups with condensed nuclei, for example the 9,10-dicarbylphenazino group and the N,N'-bisacridino group. 6. Copolymer according to claim 1, characterized in that the unit derived from an aromatic molecule is selected from groups derived from aromatic hydrocarbons and metallocenediyls, for example 9,10-bis(methylene)anthracene and 1,1'-ferrocenediyl. 7. Copolymer according to claim 1, characterized in that the comonomer polymerizable by formation of ether bonds is selected from oxymethylene, oxetane, tetrahydrofuran, methyl glycidyl ether and dioxolane. 8. Copolymer according to claim 1, characterized in that the solvating segment is selected from polyimines. 9. Copolymer according to claim 1, characterized in that at least a part of the segments A are non-sovitizing segments selected from arylene and arylalkylene radicals. 10. Copolymer according to claim 1, characterized in that at least part of the segments A is replaced by segments A' containing a group which enables the formation of a network and/or that part of the segments B is replaced by segments elements B', which do not have a redox function but carry a group that enables the formation of a network. 11. Material containing a salt and a solid polymeric solvent, characterized in that the polymeric solvent is composed according to claim 1. 12. Material according to claim 11, characterized in that the copolymer is cross-linked. 13. Material according to one of claims 11 and 12, characterized in that the salt is selected from the salts (1/mM)⁺X³⁻, where M represents a proton, an ion of a metal with valence m, selected from alkali metals, alkaline earth metals, transition metals and rare earths, or an ammonium, amidinium or guanidinium ion ; where X³ represents an anion with a delocalized electrical charge, e.g. Br⁻, ClO₄⁻, AsF₆⁻, RFSO₃⁻, (RFSO₂)₂N⁻, (RFSO₂)₃C⁻ or (RFSO₂)₂CY¹⁻ where RF represents a perfluoroalkyl or perfluoroaryl group and Y¹ represents an electron-attracting group. 14. Electrochemical generator comprising a polymeric solid electrolyte or a plasticized electrolyte or an electrolyte in the form of a gel consisting of a polymer and a liquid solvent, characterized in that at least one of its electrodes contains a segment copolymer according to claim 1. 15. A light modulation device comprising a negative electrode consisting essentially of a segmented copolymer according to claim 1.